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What options do we have for powering electric circuits without access to electric grid? For instance, to power a 10 watt LED lighting at night? The motivation to the project is to add some lighting in places where it is expensive to connect to mains.

In warm countries like Spain, southern USA, Italy etc this is a no-brainer: you just need a cheap solar panel, one cheap lead-acid battery and controller. Costs like couple of hundreds of euros/dollars at maximum, and is economically feasible if compared to mains connection (which might cost thousands of euros/dollars with excavation work etc).

But in cold countries (like here in Finland) there are plenty of problems in winter:

  • The solar panel gets covered with snow
    • And even if you place it so that it does not, the power output is negligble
  • So, a feasible solution would be to use large amount of lead acid battery capacity to get over the winter (basically December, January and February).
    • But there is a but: lead acid batteries lose their capacity in cold and in addition, you can not use even this reduced capacity because the battery will freeze and break down if it is too cold. For instance, a fully charged lead-acid battery will freeze at -70 °C (which is not a problem), but a battery with 50 % SOC will freeze in about -26 °C, which can happen here in Finland (this cold it is not very common in souther Finland but it is possible, for couple of days).

Is there any feasible alternative ways to solve the problem? The best option I've found so far is methanol fuel cell, the lowest power systems cost 3000-4000 euros/dollars so it is still cheaper than a mains connection.

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closed as too broad by Andy aka, Elliot Alderson, Dave Tweed Jun 27 at 11:23

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

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    \$\begingroup\$ Your goal is to have light am I correct? Then why does there need to be a conversion of energy involving electricity? Why not use a gas powered camping light in winter and optionally a solar powered LED light in summer? \$\endgroup\$ – Bimpelrekkie Jun 27 at 8:40
  • \$\begingroup\$ You want a automated light for night, deployable anywhere and cheap right? Does not exist. You are limited to the situation where its deployed with a choice of renewables we currently have on the market. \$\endgroup\$ – sidA30 Jun 27 at 8:45
  • \$\begingroup\$ Using gas light is a good idea, but there are no vandal-proof gas light fixtures on the market. \$\endgroup\$ – Vesa Linja-aho Jun 27 at 9:01
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    \$\begingroup\$ This means it's the perfect opportunity to make some money by creating one. \$\endgroup\$ – Janka Jun 27 at 9:23
  • \$\begingroup\$ Your question says nothing about requiring a "vandal-proof" solution. You should edit the question to add that information and explain what sort of vandals you expect. \$\endgroup\$ – Elliot Alderson Jun 27 at 10:56
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You want electricity. What you want it for is kind of irrelevant. You want it, and for your own reasons, you're looking at solar as a starting point.

Solar is lovely when space is plentiful and light isn't a problem. But storage of electricity isn't reliable at the temperatures you're looking at. So other options are: temperature controlled environment for the batteries or generate it on demand.

Generating on site is the easiest method. After all, that's what is done in out of the way places such as here.

But that has it's own problems, costs and environmental issues.

Or you could do wind generation, which is often able to give you more energy per unit cost than solar (YMMV). But again, you're limited to when and where the wind is blowing.

Don't underestimate controlling the environment of the batteries. They generate heat when current is flowing, in or out. They are resistors in a way. So, turn that heat to your advantage. You haven't supplied all the numbers for current, voltage and power consumption. But the batteries will generate heat when used, not enough to keep them warm at ex teams, but it's something. Here's an idea: make a very will insulated box, put a small heater set to keep the box at +5C. Power the heater from some cheap fossil fuel, or, if you can be confident of the power from wind, perhaps that will be enough to power an electric heater. Clearly that depends on your set up, requirements and location etc.

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